import turtle

__Pen = turtle.Pen()

List = 0
try:
    List = (1 / List)
    except ZeroDivisionError:
        __Pen.circle(50)
            __Pen.left(90)
                List += 1
                    if (List == 4):
                            print('欢迎来到源码世界！')
                                else:
                                        __Pen.circle(50)
                                                __Pen.left(90)
                                                        List += 1
                                                                if (List == 4):
                                                                            print('欢迎来到源码世界！')
                                                                                    else:
                                                                                                __Pen.circle(50)
                                                                                                            __Pen.left(90)
                                                                                                                        List += 1
                                                                                                                                    if (List == 4):
                                                                                                                                                    print('欢迎来到源码世界！')
                                                                                                                                                                else:
                                                                                                                                                                                __Pen.circle(50)
                                                                                                                                                                                                __Pen.left(90)
                                                                                                                                                                                                                List += 1
                                                                                                                                                                                                                                if (List == 4):
                                                                                                                                                                                                                                                    print('欢迎来到源码世界！')